Itaipu reservoir: impacts on the ichthyofauna and biological bases for its management

Abstract

Introduction -

Impoundments are the main source of human interference of Brazil s continental waters. Initially built to supply water for domestic and agricultural use, dams have increasingly become important for their ability to generate electricity. Improvements in excavating technology has led to a great increase in dam sizes and has enabled large rivers to be impounded. Hydroelectric reservoirs in eastern Brazil are changing the main water courses in the south, southeast and eastern regions, impounding large areas in the basins and interfering with the natural regime of floods in areas not yet inundated. -

The hydrological and limnological regime of the Brazilian section of the Paraná River has been considerably altered in the past decades. In this case, the increase in number and scale of impoundments, intensification of agriculture, industries, and large cities, have all contributed to this process. At the beginning of the 1960s, the total dammed area was about 1,000 km2. By the end of this century, considering only the larger reservoirs, this area will be close to 20,000 km2 (figure 11.1). The larger tributaries of the Paraná River, like the Grande, Tietê, Paranapanema and Iguaçu rivers have been greatly changed by hydroelectric reservoirs. The Paraná River, which extends about 800 km into Brazilian territory, has only about 500 km left free and half of that will be modified by the Porto Primavera reservoir (Centrais Energéticas de São Paulo), to be completed in 1995. The Ilha Grande Hydroelectric project (ELETROSUL), whose construction has been suspended, would eliminate the last lotic reach of this river upstream from the Itaipu reservoir. -

The diversity of fish in the Paraná River Basin is among the greatest in the world. The area, which has sustained a promising fishery industry, has unfortunately been subjected to increasing alteration of its habitat. Some species have disappeared from the basin s higher reaches and are now only in relatively undisturbed areas such as in the 300 km upstream from Itaipu reservoir. The growth of human communities in this region also poses a grave threat on the fish. For ethical and social reasons, the hydroelectric operators, the government and research institutions, should implement effective managerial action to assure the survival of those fish. In context, this paper intends to discuss some of the fish fauna alterations since the construction of the Itaipu reservoir. It will also look at the region s commercial fisheries and biological information on the main species caught by those fisheries [...]. -

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